Societies and Academies

Abstract

PARIS. Academy of Sciences, Sept. 26.—M. Duchartre in the chair.—On the white rainbow, by M. Mascart. A new mathematical treatment of the subject shows that the diameter of drops giving the most perfect achromatism is 29.17μ. With drops of 30μ the rainbow will appear the whiter, the more the apparent diameter of the sun hides the excess of blue intermediate between the achromatised points, as well as all the supernumerary arcs, by the superposition of several systems of fringes, so that there is only left an exterior border slightly tinged with red. The same will apply to drops slightly different in one sense or the other, but the achromatism persists longer if the diameter diminishes. The observation of clouds and fogs has shown that the diameter of the drops varies from 6 to 100μ, the last beginning to fall as rain. Thus the circumstances favouring the production of white rainbows are of very frequent occurrence.—Places of origin or emergence of the great cholera epidemics, and particularly of the pandemic of 1846–49, by M. J. D. Tholozan. From Dr. Arnott's communications to the Physico-medical Society of Bombay, from the documents of the Medical Committee of Bengal, and from the testimony of Ferrier, who was travelling in Afghanistan at the time, it is evident that the cholera epidemic which invaded Europe and America in 1847, 1848, and 1849 originated in Bokhara, whence it spread to Afghanistan and India, as well as westward. Bokhara, Samarkand, Balkh, and Kunduz were attacked at the end of the summer of 1844, Herat and Kabul in October, Jellalabad at the beginning, and Peshawur at the end of November. In the following summer the epidemic proceeded steadily eastwards into the “endemic area,” reaching Jhelum and Lahore in May, 1845, Meerut in August, and Delhi and Agra in October, at the same time passing down the Indus to Kurrachee, and westwards to Meshhed, whence it proceeded in 1846 to Asterabad, Teheran, Recht, and Baku. A similar example of an eastward progress of cholera occurred in 1865, when the great epidemic of Mecca, after having invaded Mesopotamia and Transcaucasia, spread to Teheran, and took the easterly route by Khorassan. The writer expresses his firm conviction that the points of emergence of the choleraic epidemics must be considered as their points of origin. The idea that the different pandemic manifestations of cholera which have depopulated Europe must have invariably come direct from India is no longer tenable. For Europe alone, two striking examples, in 1852 and 1869 respectively, have formally demolished the theories which regarded only things coming from the East as bearing any danger of contamination. The epidemic of 1852 came from within Poland and Germany. That of 1869-73 repeated the same things in Ukraine. Nowadays, when these facts have taken their place in science, some minds seek to diminish their importance by pointing out that these epidemics revived some previous epidemics which had their origin in India. But that which makes the spreading epidemic or the pandemic is the revival of the choleraic principle or germ with all its original attributes. Even in India similar revivals perpetuate the annual endemic,and the epidemics which appear every three, four, or five years. This is the main fact which governs the entire history of cholera, and upon which micro-biological research must proceed. What difference of morphology, of virulence, or of reproductive faculty is there between the germs of the epidemics which die out at their origin, and those of the epidemics which revive several times, and can invade the whole world without proceeding from India?—Application of a conventional system of rectangular co-ordinates to the triangulation of the coasts of Corsica, by M. Hatt. The trigonometrical network drawn for the hydrographic mapping of the coasts of Corsica describes a closed curve. The employment of the conventional system, which transforms into rectangular plane co-ordinates the polar co-ordinates reckoned on the sphere round an origin, offers numerous advantages. The suppression of the sphericity permits the application of processes of calculation which have been dealt with' in a preceding communication on rectangular co-ordinates. On this account it was interesting to test on a larger scale the methods which had only been utilised for the determination of secondary points. The experiment has given satisfactory results, and exhibits the practical advantages of the new system of co-ordinates and the methods of calculation. K being the length of the geodetic line joining a point to the origin, and Z the angle made by this line with a fixed direction, the conventional co-ordinates are x = K sin Z and y = K cos Z. These assumptions permit the rapid and easy calculation of tables of corrections.—On a new hydro-carbon, suberene, by M. W. Markovnikoff.—Action of piperidine and pyridine on the haloid salts of cadmium, by M. Leopold Hugo.